1. Field
The present invention relates to improvements of an electric vehicle in which left and right drive wheels are driven respectively by electric drive units.
2. Description of Related Art
Electric vehicles which can easily achieve energy saving and reduction in environmental load are attracting attention and are being put to practical use. As a result of improvements in performance of electric motors, there has been proposed a drive method in which one electric motor drives one drive wheel, as described, for example, in FIG. 1 of Patent Document 1 (Japanese Patent Application Publication No. 2006-248417).
Note that an electric motor, a hydraulic motor, and a pneumatic motor are collectively referred to as motors. When there is a need to specify the type of the motor, a term of electric motor is used.
As shown in FIG. 1 of Patent Document 1, a drive wheel (10) (the number in parentheses indicates reference numeral described in Patent Document 1. The same shall apply hereinafter) is driven by an in-wheel motor (20). The in-wheel motor (20) is an electric motor unit with a reducer in which a gear reducer is integrated with an electric motor, and is disposed in a bowl-shaped recessed portion of a wheel (13). Moreover, the drive wheel (10) is suspended from a vehicle body frame via a suspension device and moves vertically relative to the vehicle body frame. This secures ride quality.
The output is sometimes increased due to demand for high-speed travelling of the vehicle and further increase in performance of the vehicle. The output can be easily increased by increasing the size of the in-wheel motor (20).
However, the in-wheel motor (20) with an increased size cannot be fully housed in the bowl-shaped recessed portion of the wheel (13) and most of the in-wheel motor (20) protrudes from the bowl-shaped recessed portion to a vehicle body center side.
This protrusion largely affects the design of the wheel suspension device and leads to increase in design cost.
In view of this, there is a demand for an efficient suspension device and an optimum arrangement of the electric motor in a case where the electric motor cannot be disposed in the recessed portion of the wheel.